( 694 ) 
to and from the organ would also have to be reckoned with. The 
mere increase or decrease of tannin in a seedling or a vegetable 
organ' will not supply data of any value for the solution of the 
problem of the significance of tannin as a plastic material. 
Hitherto botanists have chosen the higher plants for the study 
of the physiological, significance of tannins. For the study of 
complicated vital processes and of the physiological significance of 
chemical constituents certain lower plants appear to me to offer 
advantages above those of the higher ones, the structure of which 
is so much more complicated. For such an investigation the thicker 
species of the genus Spirogyra seem particularly suitable. It is true 
that the tannin of Spirogyra lias not yet been examined chemically, 
but numerous microchemical reactions allow us to conclude with a 
fair degree of certainty that Spirogyra contains in its cell sap a 
considerable quantity of tannin. De Vries ') has proved this, after 
abnormal plasmoiysis, with various tannin reagents e. g. ferric salts, 
potassium bichromate, osmic acid. In addition to these reagents many 
others- also give in the cell ^sap precipitates which agree completely 
with those caused in tannin solutions. 
The advantages which the thicker species of Spirogyra have over 
the higher plants are the following. Pieces of the filaments may be 
examined microscopically without killing them or damaging them, 
and the changes m the cells can be studied in the living plant. They 
are particularly suited to all sorts of experiments. They are not too 
small to be handled and not too thick for microscopic examination. 
The various constituents of the cell can readily be observed under 
the microscope. As in .he case of unicellular Algae a transport of 
. 0 m f ena rom one cell to another is very probably excluded 
whffTT' ! imp0r,ant fae,or ’ which must be taken into account 
when dealing w„h the higher plants, need generally not be considered 
U™, fv e m<sans of the centrifuge all sorts of 
nnX,? n maj r be ° btained ’ Sach as polynuclear cells, cells without 
tV: : , a Urge a " d With a sma11 chrotnatophores-mass, 
the LtillL ' chroma,0 P hores - In this way we can eliminate 
carbon from Process, t. e. the intake by the ehromatophores of 
W * P Carb °" di ° xide under the i^ence oflight. 
wMrh t 'T a u' mber ° f eom P ara, t' ve experiments may be made 
» the case of the higher plants, and because 
J^T mWh 8 ’ T Wandd “ V ah“»Ien,Pringsh. 
van Spirogyra nitida MaanHW a * Heft P- 57 &. Over looistofreactien 
p. 7. ' Maandblad T00r Natuurwetenschappen, 1886, N*. 7, Reprint 
